Fluid pressure calculator

Formula

How it works

Going deeper into a fluid adds the weight of the fluid above pressing down, which grows with depth, the fluid's density and gravity. That extra pressure is the gauge pressure; adding the pressure already present at the surface gives the absolute pressure.

Worked example

The same calculation with the default values:

• Fluid density 1,000 kg/m³
• Depth 10 m
• Pressure at the surface 101,325 Pa

1. gauge pressure P = 1,000 × 9.80665 × 10 = 98,066.5 Pa
2. absolute pressure P = 101,325 + 98,066.5 = 199,391.5 Pa

Result: Gauge pressure: 98,066.5 Pa · Absolute pressure (Pa): 199,391.5 Pa · Absolute pressure (atm): 1.96784111 atm

Common mistakes

• Forgetting to add atmospheric pressure (P₀) when the absolute pressure is needed - this formula gives gauge pressure from the fluid column alone unless P₀ is explicitly included.
• Using the wrong fluid density - pressure at depth depends directly on the fluid's density, so using water's density for a different fluid (seawater, oil) gives a noticeably wrong result.
• Confusing depth below the surface with total height of fluid in a container - the relevant variable is always the vertical depth below the free surface, not a container's total height.